Element Resistant to Air Transfers and Thermal and Hydric Transfers in the Field of Construction, Especially for Lightweight Walls or Lightweight Facades

ABSTRACT

An element is directed to the dry construction of lightweight walls, especially the construction of load-bearing lightweight façades or non-load-bearing lightweight façades, which do not contribute to the stability of the building. The element includes a panel based on a hydraulic binding agent and all or part of the face is coated with a polymer film obtained by polymerization under the action of radiation. The element also includes a structure, and a jointing component resistant to air transfers and thermal and hydric transfers. The element does not comprise any membranes that are resistant to air transfers and thermal and hydric transfers.

The present invention relates to the dry construction of lightweight walls, especially the construction of load-bearing lightweight façades or non-load-bearing lightweight façades, that is those which do not contribute to the stability of the building.

The façade of a building represents its shell and has the role of creating an interface between the interior of the building and the exterior. Non-load-bearing lightweight façades are façades constructed with lightweight industrial materials, on a building framework as opposed to a traditional construction with a concrete wall and with infilling by masonry or the like. The non-load-bearing lightweight façades are borne by the structure of the building, which is referred to as the load-bearing structure. By definition it is understood that the load-bearing structure is supported on the foundations. The non-load-bearing lightweight façades are fixed to the load-bearing structure by means of a framework known as a primary framework. Non-load-bearing lightweight façades may themselves comprise, when necessary, a framework which is called the secondary framework, fixed to the primary framework. The load-bearing lightweight façades on the other hand are borne directly by the foundations.

The façades and all the joints thereof (between frames, between frame and infill, between frames and sealants on the main structure, between window frames and sashes, etc.) in the conditions inherent in the construction and, taking into account the effects of wind and rain, must ensure the impermeability to water between the interior and exterior environments. The impermeability to water is defined by the Standard NF EN 12154 as the absence of penetration of water which would continuously or repeatedly wet:

-   -   parts of the interior face of the element being tested;     -   any part of the element tested which is intended to remain dry         and does not form part of the system of drainage to the         exterior.

The protection of the façades with respect to water is therefore an important point and the impermeability to water cannot be ignored. In fact, the penetration of the water can cause the degradation of the interior coatings of walls, the deterioration of the energy performance of the façade, and also the breakdown of frost-susceptible materials. When the façade separates an exterior environment from an interior environment, with a water vapour pressure greater than the interior, the water vapour contained in the interior air will tend to migrate towards the exterior. Passing through the infill of the façade, the water vapour can encounter a temperature which is low enough to cause it to condense at the location where the temperature is equal to the dew point. The presence of humidity could then alter the material, the bonding, and impair the insulation performance of the façade, and this damage is aggravated by the alternating cycles of humidification and evaporation.

In order to avoid this phenomenon of condensation, it is possible to choose the nature and the arrangement of the infill materials as a function of the climate, by adding on site one or more membranes and/or by applying one or more resins or polymer films to the materials in order to obtain the impermeability to vapour, to air, to wind and/or to rain.

Membranes may be applied facing the cavity of the façade on the inside of the building, in order to prevent the maximum water vapour penetration into the infill (vapour barrier).

Membranes may be applied at the level of the façade on the outside of the building, in order to prevent the maximum wind and rain penetration into the infill (wind barrier and rain barrier). A wind barrier and rain barrier has the advantage of improving the impermeability of the building to air and to water by preventing rain and wind from penetrating into the building and thus impairing the insulating properties of the components of the building and their durability. This makes it possible to contribute to the improvement of the energy efficiency of the building.

The drawback of such membranes or resins resides in their lack of reliability in terms of impermeability to air and to water. In fact, joining of the membranes to one another and also fixing them causes losses of impermeability which alters the thermal performance of the building and decreases the reliability in terms of impermeability. Moreover the application on site of these membranes or these resins is a supplementary step for the installer, a step which consumes time and which decreases the productivity on site. Finally, these membranes can be easily perforated during the construction of the building.

In order to meet the requirements of installers, it has become necessary to find another means of discontinuing the installation of these membranes or the application of these resins on site whilst retaining the properties which they confer.

Also the problem which the invention seeks to solve is to provide a new mean suitable for building lightweight façades which are resistant to transfers of air and to thermal and hydric transfers avoiding the drawbacks mentioned above.

Unexpectedly the inventors demonstrated that it is possible on site to omit installation of the membranes or application of the resins which are impermeable to transfers of air and to thermal and hydric transfers.

To this end the present invention relates to an element resistant to air transfers and thermal and hydric transfers in the field of construction, comprising:

-   -   a panel based on hydraulic binder, all or part of the face of         which is coated with a polymer film obtained by polymerisation         under the action of radiation;     -   a framework;     -   a jointing component resistant to transfers of air and to         thermal and hydric transfers;         said element does not include any membrane resistant to         transfers of air and to thermal and hydric transfers.

The invention also proposes the use of the above element in order to produce a lightweight façade.

The invention also proposes a lightweight façade comprising at least the element described above.

Finally the invention also relates to the use of a panel based on hydraulic binder of which the facing is coated entirely or partially with a polymer film obtained by polymerisation under the action of radiation such as a steam barrier, rain barrier or wind barrier.

The invention offers at least one of the decisive advantages described below.

Advantageously, the element according to the invention makes it possible to maintain the impermeability to water or to air of the façade in which said element is incorporated and to increase the reliability in terms of impermeability of this façade.

Another advantage of the element according to the invention is that it makes it possible to omit on site the step of application of membranes or of resins, which step consumes time and decreases the productivity on site.

Moreover, the element according to the invention enables a great rapidity of installation on site.

The element according to the invention offers as another advantage that it can also be used for the construction of load-bearing lightweight façades, that is those which contribute to the stability of the building, in particular the constructions in North America on lightweight structures made for example of metal or wood.

Other advantages and characteristics of the invention will become clear when reading the following description and the examples given for purely illustrative and non-limiting purposes.

The expression “lightweight façade” is preferably understood according to the present invention as a façade comprising one or multiple walls, of which at least one exterior wall is characterised by:

-   -   a low mass, almost always less than about 100 kg/m² (compared         with more than 200 kg/m² of opaque walls of façades produced in         masonry or in concrete);     -   the use of manufactured products generally equipped with         finished facings.

The lightweight façade can be selected from among curtain walls, integral curtain walls, vertically extending curtain walls, semi-curtain walls, integral semi-curtain walls, vertically extending semi-curtain walls, panel façades and horizontally extending panel façades. All these terms are defined in the standard NF P28-001.

The expression “load-bearing structure” is preferably understood according to the invention to mean all of the elements of a construction bearing more than their own weight. As an example of an element which can be load-bearing, mention may be made of posts, shear walls, floors, walls.

The expression “primary framework” is preferably understood according to the invention to mean all of the uprights and cross-members made of wood or of metal or of synthetic material fixed on the load-bearing structure of the construction or on the foundation and serving as support for elements of the construction such as infill elements. By way of example mention may be made of sub-frames. It should be noted that in certain particular cases the primary framework can be the load-bearing structure, as is the case in North America (in English, the term “load-bearing frame” is used in this case).

The expression “secondary framework” is preferably understood according to the invention to mean all of the uprights and cross-members made of wood or of metal or of synthetic material, directly fixed on the primary framework or on the foundation and serving as support for structures, frames, infills or a cladding.

The expression “jointing component” is preferably understood according to the invention to mean a device which can ensure the continuity of the impermeability to water, to water vapour or to air.

The expression “resistant to transfers of air and to thermal and hydric transfers” is preferably understood according to the invention to mean a material or product having a controlled permeability of thermal, hydric and/or air transfers.

The expression “hydraulic binder” is preferably understood according to the present invention to mean any compound having the property of hydration in the presence of water and of which the hydration makes it possible to obtain a solid having mechanical characteristics. The hydraulic binder according to the invention may in particular be a hydraulic binder based on calcium sulphate. The hydraulic binder according to the invention is preferably plaster.

The expression “hydraulic binder based on calcium sulphate” is understood according to the invention to mean the partially anhydrous or totally anhydrous hydraulic binders based on calcium sulphate.

The following terms are preferably understood according to the present invention as follows:

-   -   CaSO₄.2(H₂O) for gypsum or calcium sulphate dihydrate;     -   CaSO₄.0.5(H₂O) for calcium sulphate hemihydrate or partially         anhydrous calcium sulphate;     -   CaSO₄ for anhydrous calcium sulphate or calcium sulphate         anhydrite (type II or type III) or totally anhydrous calcium         sulphate.

The term “plaster” is preferably understood according to the invention to mean both calcium sulphate in its form CaSO₄.0.5(H₂O) and in its form CaSO₄.2(H₂O) after hydration (such as for example for a plaster panel).

First of all the present invention relates to an element resistant to air transfers and thermal and hydric transfers in the field of construction, comprising:

-   -   a panel based on hydraulic binder, all or part of the face of         which is coated with a polymer film obtained by polymerisation         under the action of radiation;     -   a framework;     -   a jointing component resistant to transfers of air and to         thermal and hydric transfers;         said element does not include any membrane resistant to         transfers of air and to thermal and hydric transfers.

The element according to the invention is an element resistant to transfers of air and to thermal and hydric transfers, that is to say that this element has a controlled permeability to transfers of air, of water in the form of vapour or of liquid.

The panel based on hydraulic binder suitable for the element according to the invention can be a panel of cement or a panel of plaster, and this panel is preferably prefabricated in a prefabrication factory.

The cement panels suitable for the element according to the invention may be based on portland cement, cement described in accordance with the standard EN 197-1, cement of the calcium aluminate type, magnesium cement or sulphoaluminate cement and mixtures thereof. Cements based on calcium aluminates such as for example alumina cements or Ciments Fondus® are also suitable according to the invention as well as cements according to the standard NF EN 14647. The preferred magnesium cements comprise magnesium carbonates, magnesium oxides or magnesium silicates, for example as described in U.S. Pat. No. 4,838,941. The preferred cement according to the invention is portland cement, alone or in a mixture with other cements referred to above, for example sulphoaluminate cements. The portland cement which is particularly suitable according to the invention is the one described according to the standard EN 197-1. The cement panels can be produced by various processes and in particular by non-continuous processes (for example moulding, pressing, filtering etc.). Cement panels referred to as lightweight because of the incorporation of lightweight fillers are also suitable for the element according to the invention. These lightweight fillers are generally derived from natural rocks or artificial rocks or are fillers derived from petroleum products, for example polystyrene beads. Cement panels reinforced by the incorporation of fibres are also suitable for the element according to the invention.

The plaster panels suitable for the element according to the invention may be composed of a body of plaster cast in the factory between two sheets of paper constituting both its facing and its reinforcement. In general one of the foil of paper used in order to manufacture the plaster panels is of a dark colour which can vary between a grey colour and a brown colour since it is composed of cellulose fibres which have not undergone any particular purification treatment. Conventionally, this grey paper is obtained on the basis of unbleached chemical pulp, and/or mechanical pulp, and/or thermomechanical pulp, and/or semi-chemical pulp. Mechanical pulp is generally understood to be a pulp obtained entirely by mechanical means from various raw materials, essentially wood, which can be provided by recovered products derived from wood such as old cardboard, offcuts of kraft paper and/or old newspapers. Thermomechanical pulp is understood to be a pulp obtained by heat treatment followed by a mechanical treatment of the raw material. Semi-chemical pulp is understood to be a pulp obtained by eliminating a part of the non-cellulose components contained in the raw material by means of a chemical treatment, necessitating a subsequent mechanical treatment in order to disperse the fibres. The other sheet of paper used in order to manufacture the plaster panels has a visible face known as the facing, generally of a lighter colour than the grey sheet.

The panel based on hydraulic binder which is suitable for the element according to the invention is preferably a plaster panel having a gypsum core of which the density can evolve as a function of the distance relative to the surface, with for example a layer of low-density core including foaming agents in the pulp, this core layer being sandwiched by high-density surface layers (dense layer). An example of this type of panel is the conventional plaster panel of the BA13 type with dense layers.

The panel based on hydraulic binder which is suitable for the element according to the invention can comprise an anti-fungal agent.

The panel based on hydraulic binder which is suitable for the element according to the invention can comprise a water-repellent agent.

The panel of hydraulic binder which is suitable for the element according to the invention comprises at least one facing. The conventional facings used in the manufacture of plaster panels are quite particularly suitable such as for example facings made of cellulose fibre. Mention may be made for example of facings made of cellulose fibres (paper, recycled paper), synthetic fibres (polyester, polypropylene, polyethylene etc.) or inorganic fibres (facings made of glass fibre, ceramic fibres, etc.). The facings may be woven or non-woven. The fibres are generally joined together with the aid for example of a heat-sensitive or hot-melt resin such as urea formaldehyde resins, acrylic resins, melamine formaldehyde resins with or without additions of urea or polyvinyl acetate resins. Likewise it may be envisaged to add lightweight fillers between the fibres. For example, the facings sold by the Johns Manville international, Inc. or sold by Ahlstrom are suitable according to the invention.

According to one variant, the panel of hydraulic binder which is suitable for the element according to the invention can be coated on one face, entirely or partially, with a metallised plastic film reflecting the infrared radiation. By way of metallised plastic film, mention may be made of metallised polyethylene terephthalate or the metallised polyester. For example, survival blankets could be used for coating one side of the panel of hydraulic binder which is suitable for the element according to the invention.

According to another variant, the panel of hydraulic binder which is suitable for the element according to the invention can be coated on one face, entirely or partially, with a plastic film.

According to another variant, the panel of hydraulic binder which is suitable for the element according to the invention can be coated on one face, entirely or partially, with a plastic film.

The panel of hydraulic binder which is suitable for the element according to the invention is coated, entirely or partially with a polymer film obtained by polymerisation under the action of radiation. This type of polymer film obtained by polymerisation under the action of radiation is likewise known as photo-crosslinked polymer or cross-linkable film-forming resin or photosensitive resin.

A composition of monomers and/or of non-polymerised reactive prepolymers is applied entirely or partially on the facing of the panel of hydraulic binder. This composition of monomers and/or of non-polymerised reactive prepolymers can be based on the following precursors:

-   -   a prepolymer based on a resin comprising at least one         unsaturated group such as the acrylate, methacrylate, allyl,         vinyl, epoxy group and/or mixtures thereof such as for example         an acrylic resin, a methacrylic resin, a polyester resin, a         chlorinated polyester resin, an epoxy resin, a melamine resin, a         polyamide resin, a silicone resin, a polyether resin, a         polyurethane resin, a polyurea-urethane resin and/or mixtures         thereof. Among these resins, the resins comprising the acrylate         group may be partially modified by the action of an amine. Among         these resins, the polyurethanes comprise acrylate groups and the         epoxides comprising acrylate groups are particularly preferred         according to the invention.     -   a monomer comprising at least one reactive group, for example an         unsaturated group. By way of reactive groups mention may be made         for example of the acrylate, methacrylate, allyl, vinyl, epoxy         group and/or mixtures thereof. Amongst these monomers the         acrylic esters of alcohols such as isobornyl acrylate (IBOA),         diols such as diethylene glycol diacrylate (DEG), tripropylene         glycol diacrylate (TPGDA), bisphenol A diacrylate, or polyols         such as trimethylolpropane triacrylate (TMP), glycerol         propoxylate triacrylate (GPTA), pentaerythritol tri- and         tetra-acrylate, can be used according to the invention. Methyl         pentanediol diacrylate (MPDDA) is particularly preferred         according to the invention.     -   a photoinitiator, such as for example mixtures of derivatives of         benzophenone and tertiary amines or cationic systems such as         triphenylsulphonium hexafluoroantimonate or such as for example         a mixture of oxide acyl phosphines such as Irgacure™ 819 (BAPO)         or Darocur™ TPO (mono acyl phosphine (MAPO)), the Darocure™ 4265         (mixture of MAPO and α-hydroxyketone 50/50) sold by Ciba and         α,β-disubstituted α-hydroxy acetophenone.         2-hydroxy-2-methyl-1-phenyl-propan-1-one (Darocure™ 1173, sold         by Ciba) and 1-hydroxycyclohexyl-phenylketone (Irgacure™ 184,         sold by Ciba) are particularly preferred according to the         invention.

One of the preferred compositions according to the invention of monomers and/or of non-polymerised reactive prepolymers comprise:

-   -   epoxy acrylate oligomer     -   methyl pentanediol diacrylate (MPDDA)     -   urethane acrylate oligomer     -   2-hydroxy-2-methyl-1-phenyl-propan-1-one or         1-hydroxy-cyclohexyl-phenylketone.

The composition of monomers and/or of non-polymerised reactive prepolymers can comprise from 1% to 10% by mass of photoinitiator, preferably from 2% to 8% and more preferably from 3% to 6%.

The composition of monomers and/or of non-polymerised reactive prepolymers can be prepared by simple mixing of its components with the aid of any type of mixer. The mixture obtained is stable and it can be kept for several months at ambient temperature and away from direct sunlight.

The composition of monomers and/or of non-polymerised reactive prepolymers is applied entirely or partially on the facing of the panel with the aid of an applicator roller, a brush or a sprayer or any other means enabling a fine layer of composition to be deposited on the facing. This application can take place during or after the manufacture of the panel of hydraulic binder.

The composition of monomers and/or of non-polymerised reactive prepolymers can be applied din one or more layers. The total thickness of said composition deposited on the facing is preferably from 5 to 100 microns, more preferably from 10 to 60 microns and still more preferably from 15 to 50 microns. Polymerisation may or may not be effected between the layers. According to a preferred variant of the invention the composition of monomers and/or of non-polymerised reactive prepolymers is applied in two layers of 20 microns with a polymerisation between the two applications, instead of the application of one single layer of 40 microns.

The polymerisation of monomers and/or of reactive prepolymers takes place under the action of radiation, preferably under the action of waves of which the wavelength is located in the visible ultraviolet spectrum, or of which the wavelength is even shorter. It may likewise be envisaged that the polymerisation takes place under the action of infrared radiation. The radiation causes the polymerisation by condensation reactions or addition of precursors of the polymer, in particular the radiation causes the crosslinking of the precursors of the polymer. It may likewise be envisaged that the polymerisation takes place under the action of an electron beam. In this case, the composition of monomers and/or of non-polymerised reactive prepolymers does not comprise a photoinitiator, since the energy of the electron beams is sufficient in order to create the free radicals necessary for the polymerisation.

The polymer film is preferably obtained by the polymerisation under the action of ultraviolet radiation. The ultraviolet rays (UV) make it possible to exciter or to break down the photoinitiator and to cause the formation of free radicals or of ions and which leads to the polymerisation of the prepolymer with the monomer.

The polymerisations may be conducted at a rate of passage under the UV lamp of 5 metres/minute to 30 metres/minute. The total dose of energy received (once or more times if necessary) by the composition of monomers and/or of reactive prepolymers is preferably from 300 to 1200 mJ/cm².

The polymerisation may be conducted in the presence of an inert gas, such as nitrogen, making it possible to reduce the quantities of photoinitiator in the composition, and likewise to harden the surface of the polymer film.

The polymerisation causes the formation of the polymer film. This polymer film is preferably continuous. According to a first variant, this polymer film is only located on one side of the panel of hydraulic binder. According to a second variant, the 2 sides of the panel of hydraulic binder are coated entirely or partially by the polymer film.

In particular, one side of the panel of hydraulic binder is coated entirely by the polymer film.

According to another variant of the invention, it is possible to apply two or more polymer films, one on top of the other, on the facing of the panel of hydraulic binder. Consequently the performance of the panel of hydraulic binder is improved.

The polymer film may also comprise an anti-fungal agent, a colouring agent, of pigment, an agent or a mineral filler which makes it possible to improve the adhesion of a sealant or of paint or of any other surface application capable of being deposited on the panel of hydraulic binder (such as for example silica, calcium carbonate, titanium dioxide, magnesium carbonate, calcium sulphate, magnesium oxide, calcium hydroxide or a powdered solid).

The element according to the invention which is resistant to air transfers and thermal and hydric transfers in the field of construction comprises at least one framework. This may be secondary or primary. This framework can be made of metal, fibre cement, wood, composite material or synthetic material. This framework can be a metal structure, an upright or a rail.

The jointing component of the element according to the invention can be in high parts, in low parts or in lateral joints, and it ensures the continuity of the performance fulfilled by the façade. This continuity should be ensured even when subjected to the known stresses of the building, enabling the foreseeable differential behaviour of the elements and taking account of manufacturing and installation tolerances of these different elements. This jointing component makes it possible to guarantee maximum sealing of the element according to the invention.

This jointing component can be chosen from amongst a jointing coating, a mastic (see for example NF DTU 44.1), a bituminous coating and a self-adhesive strip resistant to transfers of air and to thermal and hydric transfers.

In the case of a jointing coating, this latter can comprise at least mineral fillers, water, a hydrophobic agent, an anti-fungal agent and/or a polymer. The hydrophobic agent can be for example a derivative of silicone. This agent in particular enables a better resistance to damage by water vapour. The jointing coating can also comprise an organic binder which is dispersible in an phase aqueous, for example polyvinyl acetates and/or acrylic acid esters. This binder can make it possible to give the coating a sufficient flexibility in order to resist mechanical stresses and at the same time to provide an adhesive power in order to obtain good adhesion on the whole surface. Furthermore, the composition of the coating includes a workability agent, in particular a water-retaining and thickening agent, for example methylhydroxyethylcellulose.

The element according to the invention can be used in order to produce a lightweight façade, a ceiling, a lining, an insulation system, or a wall, for example a separating wall, a partition wall or a countering wall.

The element according to the invention can be used in order to produce a lightweight façade. In this case the framework, the panel and the jointing component are joined to one another. Such a process is carried out for example when assembling panels of plaster coated with a facing made of cardboard with a jointing coating in order to produce the shell of a building separating the exterior from the interior, in particular lightweight façades on non-load-bearing frameworks or load-bearing lightweight structures.

A common construction technique is to fix plaster panels on a metal framework comprising horizontal rails fixed for example to the base and the vertical uprights. This technique for construction of walls is relatively simple and inexpensive.

The invention relates to the use of an element resistant to air transfers and thermal and hydric transfers in order to produce a lightweight façade comprising at least:

-   -   a panel based on hydraulic binder, all or part of the face of         which is coated with a polymer film polymerised under the action         of radiation;     -   a framework;     -   a jointing component impermeable to transfers of air and to         thermal and hydric transfers;         said element does not include any membrane impermeable to         transfers of air and to thermal and hydric transfers.

The invention also relates to a lightweight façade comprising at least one element resistant to air transfers and thermal and hydric transfers in the field of construction, comprising:

-   -   a panel based on hydraulic binder, all or part of the face of         which is coated with a polymer film obtained by polymerisation         under the action of radiation;     -   a framework;     -   a jointing component resistant to transfers of air and to         thermal and hydric transfers;         said element does not include any membrane resistant to         transfers of air and to thermal and hydric transfers.

The invention also relates to the use of a panel based on hydraulic binder, all or part of the face of which is coated with a polymer film obtained by polymerisation under the action of radiation as vapour barrier.

The invention also relates to the use of a panel based on hydraulic binder, all or part of the face of which is coated with a polymer film obtained by polymerisation under the action of radiation as rain barrier.

The invention also relates to the use of a panel based on hydraulic binder, all or part of the face of which is coated with a polymer film obtained by polymerisation under the action of radiation as wind barrier.

The following examples illustrate the invention without limiting the scope thereof.

EXAMPLES

1—Description of an Embodiment of a Panel Based on Hydraulic Binder with a Polymer Film Obtained by Polymerisation Under the Action of UV;

The following chemical compounds have been used in order to produce the panel based on hydraulic binder used in the element according to the invention:

Brand name Chemical name Photomer ™* 6010 Urethane acrylate oligomer Photomer ™* 4071 F Methyl pentanediol diacrylate (MPDDA) Photomer ™* 3016 F Epoxy acrylate oligomer Darocur ™* 1173 2-hydroxy-2-methyl-1-phenyl-propan-1-one Irgacure ™* 184 1-hydroxy-cyclohexyl-phenylketone *The Photomers are sold by IGM Resins. The Darocur and the Irgacure ™ are sold by Ciba.

composition of the formulae (% by mass) Formulae* A B C D. E: F. Photomer ™ 6010 70 70 — — Photomer ™ 6891 — — 85 70 60 74 Photomer ™ 4071 25 10 10 10 23 21 Photomer ™ 3016 — 15 — 15 12 — Photomer ™ 1173  5 — — — Irgacure ™* 184 —  5  5  5  5  5 *in percentages by mass

The compounds of the chosen formula were fed into a mixer, then agitated at ambient temperature until a homogeneous mixture was obtained. The mixture was stable and could be kept for several months at ambient temperature and away from direct sunlight. This mixture was applied to the facing of the standard plaster panels of the BA13 type with the aid of an applicator roller then left to polymerise under the action of UV radiation. The UV makes it possible to break down the photoinitiator, which leads to the polymerisation of the acrylic functions.

The polymerisation was conducted at a rate of passage under the UV lamp of 5 metres/minute to 30 metres/minute, the energy dose received was sufficient in order to obtain the most complete polymerisation possible and to avoid any adhesive effect on the surface of the polymer film.

2—Tests of Ageing by Exposure of a Panel to UV and to Humidity:

Tests of ageing by exposure to UV and to humidity in a Q-UV unit, such as that used in the standard ISO-11507, or by exposure for several month outside to bad weather and to the sun with daily watering for 2 hours, were carried out and showed a very good resistance of formulae A to F. In particular formula D did not show any visible alteration after 4 months of exposure.

Formulae E and F were less viscous, with a measured viscosity of the order of 1700 mPa·s (Brookfield LVT) compared with about 4000 mPa·s for the formulae A to D. After polymerisation by exposure to UV radiation, formulae E and F gave polymer films which were more flexible than those of formulae A to D. The application of a first layer of formula F, followed by polymerisation thereof, then the application of a second layer of the formula D or E, followed by polymerisation thereof, made it possible to obtain a polymer film which was flexible and very resistant.

Formula D was applied in two successive layers respectively of 25 microns and of 19 microns (total thickness=44 microns). The polymerisation was carried out after each layer by passage below a mercury vapour UV lamp with a nominal power of 80 Watt/cm. The rate of passage in front of the lamp was 7 metres/minute and the real dose received by the formula was 524 mJ/cm² on each passage. The sample coated with the polymer film was exposed to bad weather in outdoor conditions, with a forced watering for two hours per day. The performance and the resistance of the polymer film were assessed by the measurement of the water uptake with the aid of the Cobb test.

Duration of exposure in days 45 75 105 Formula D Cobb Test (water uptake in g/cm²) 1.33 3.0 25.0 Control (without polymer film) Cobb Test (water uptake in g/cm²) 160 779 * * The control sample was destroyed by the conditions of exposure after 105 days and no measurement was possible at 105 days. 

1-11. (canceled)
 12. An element resistant to air transfers and thermal and hydric transfers in the field of construction, comprising: a panel based on a hydraulic binder, all or part of the face of which is coated with a polymer film obtained by polymerisation under the action of radiation; a framework; a jointing component resistant to transfers of air and to thermal and hydric transfers; said element does not include any membrane resistant to transfers of air and to thermal and hydric transfers.
 13. The element as claimed in claim 12, wherein the panel based on a hydraulic binder is a selected one of a panel of cement, and a panel of plaster.
 14. The element as claimed in claim 12, wherein the polymer film is obtained by polymerisation under the action of ultraviolet radiation.
 15. The element as claimed in claim 12, wherein the framework is made from a material selected from the group consisting of metal, fibre cement, wood, composite material, and synthetic material.
 16. The element as claimed in claim 12, wherein the jointing component is a component selected from the group consisting of jointing coating, a mastic, a bituminous coating, and a self-adhesive strip resistant to transfers of air and to thermal and hydric transfers.
 17. The element as claimed in claim 12, wherein the jointing component is a jointing coating selected from at least one of mineral fillers, water, a hydrophobic agent, an anti-fungal agent or a polymer.
 18. The element as claimed in claim 12, wherein the element is one selected from a group consisting of a lightweight façade, a ceiling, a lining, an insulation system, and a wall.
 19. A lightweight façade comprising at least one element as claimed in claim
 12. 20. Use of a panel based on hydraulic binder, all or part of the face of which is coated with a polymer film obtained by polymerisation under the action of radiation, and is a barrier selected from the group consisting of a vapour barrier, rain barrier, and a wind barrier. 